We will continue our work on membrane circulation in nervous tissue, especially on the photoreceptors of the frog retina. Studies will concern: 1. lipid synthesis in rod cells as detectable by electron microscope autoradiography; 2. the influence of various divalent cations on membrane circulation in photoreceptor presynaptic terminals; 3) the uptake and sequestering of Ca2 ion by rod cell endoplasmic reticulum; 4. the uptake of peroxidase labeled cholera toxin by photoreceptors; 5. the properties of peroxisomes in nervous tissue.